The transition from calc-alkaline to potassic orogenic magmatism in the Aeolian Islands,Southern Italy |
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| Authors: | R M Ellam M A Menzies C J Hawkesworth W P Leeman M Rosi G Serri |
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| Institution: | (1) Department of Earth Sciences, The Open University, MK7 6AA Milton Keynes, United Kingdom;(2) Department of Geology, Royal Holloway and Bedford New College, Egham, United Kingdom;(3) Department of Geology and Geophysics, Rice University, 77251 Houston, TX, USA;(4) Dipartimento di Scienze della Terra, via S Maria, 53, I-56100 Pisa, Italy;(5) Present address: Department of Earth Sciences, University of Oxford, Parks Road, OX1 3PR Oxford, United Kingdom |
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| Abstract: | The Aeolian volcanic arc displays a wide range of magmatic products. Mafic lavas range from hypersthene normative calc-alkaline basalts to silica-undersaturated potassic absarokites, although the former are spatially and temporally dominant, consistent with the subduction-zone tectonic setting. In addition, intermediate and acidic members of the various fractionation series may be recognised. Large variations in trace element and isotope ratios accompany the rapid calc-alkaline to potassic transition, and it is argued that these may be largely explained in terms of subduction-zone mantle enrichment involving components derived from both basaltic ocean crust and subducted sediments. In addition, it seems that the mantle wedge itself was substantially heterogeneous prior to the onset of subduction zone processes. Not only are these subduction components similar to those proposed in a number of island arcs, but they also resemble those recognised in the ultra-potassic lavas of the Roman province, supporting recent subduction-related petrogenetic models of the Roman magmatism. Although subducted sediment plays an important role in the generation of some potassic magmatism, it is not uniquely responsible for K2O-rich lavas, which are also produced without a large sediment contribution. |
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